Integrated Circuit Device Including a Power Supply Line and Method of Forming the Same

ABSTRACT

A device includes a first semiconductor strip and a second semiconductor strip extending longitudinally in a first direction, where the first semiconductor strip and the second semiconductor strip are spaced apart from each other in a second direction. The device also includes a power supply line located between the first semiconductor strip and the second semiconductor strip. A top surface of the power supply line is recessed in comparison to a top surface of the first semiconductor strip. A source feature is disposed on a source region of the first semiconductor strip, and a source contact electrically couples the source feature to the power supply line. The source contact includes a lateral portion contacting a top surface of the source feature, and a vertical portion extending along a sidewall of the source feature towards the power supply line to physically contact the power supply line.

PRIORITY DATA

This application is a divisional application of U.S. patent applicationSer. No. 16/583,438, filed Sep. 26, 2019, which claims benefit of U.S.Provisional Patent Application Ser. No. 62/753,728, filed Oct. 31, 2018,each of which is incorporated herein by reference in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component, or line, that can be created using afabrication process) has decreased.

Despite advances in materials and fabrication techniques, scaling oftransistor devices, such as metal-oxide-semiconductor field effecttransistor (MOSFET) devices, has proven challenging. For example,although resulting in greater integration and more efficient use of chipreal estate, a reduction in feature size can result in increased contactresistance and capacitance. Additionally, process window requirementsand critical dimension requirements can become more constrained as moretransistor devices are integrated into a unit chip area. This, in turn,can lead to an increase in the complexity of manufacturing processesused to form integrated circuit devices. Improvements in integratedcircuit devices and the methods used to manufacture them may be needed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 shows a simplified layout of an integrated circuit device thatincludes an array of standard cells, in accordance with an embodiment;

FIG. 2 shows a simplified top-down schematic view of transistor devicesformed in some of the standard cells shown FIG. 1, in accordance with anembodiment;

FIG. 3 shows a zoomed-in view of a region of FIG. 2 including a firsttransistor device of a standard cell and a second transistor device ofanother standard cell, in accordance with an embodiment;

FIG. 4 shows a cross-sectional view of the transistor devices shown inFIG. 3, in accordance with an embodiment;

FIGS. 5A and 5B show zoomed-in views of a source contact and a powersupply line shown in FIG. 4, in accordance with an embodiment;

FIGS. 6A to 6Q show a process flow illustrating a method for formingtransistor devices of the array of standard cells of FIG. 1, inaccordance with an embodiment;

FIG. 7 shows a flow chart describing a method for forming transistordevices of the array of standard cells of FIG. 1, in accordance with anembodiment.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. Still further, when anumber or a range of numbers is described with “about,” “approximate,”and the like, the term is intended to encompass numbers that are within+/−10% of the number described, unless otherwise specified. For example,the term “about 5 nm” encompasses the dimension range from 4.5 nm to 5.5nm.

FIG. 1 shows a simplified layout of an integrated circuit device 100that includes an array of standard cells, in accordance with anembodiment. In semiconductor design, standard cell methodology is amethod of designing application-specific integrated circuits (ASICs)with mostly digital-logic features. Standard cell methodology is anexample of design abstraction, whereby a low-level very-large-scaleintegration (VLSI) layout is encapsulated into an abstract logicrepresentation (e.g. such as a NAND gate). Cell-based methodology—thegeneral class to which standard cells belong—makes it possible for onedesigner to focus on the high-level (logical function) aspect of digitaldesign, while another designer focuses on the implementation (physical)aspect. Along with semiconductor manufacturing advances, standard cellmethodology has helped designers scale ASICs from comparatively simplesingle-function ICs (of several thousand gates), to complexmulti-million gate system-on-a-chip (SoC) devices. In various examples,a standard cell (e.g. which may be referred to as a functional cell, afunctional logic cell, and/or a circuit region) may include a group oftransistors and interconnect structures that implement a circuit, forexample, a circuit providing a Boolean logic function (e.g. AND, OR,XOR, XNOR, NAND, NOR, inverters, etc.) or a storage function (e.g.flip-flop or latch). The simplest standard cells are directrepresentations of the elemental NAND, NOR, and XOR Boolean function,although cells of much greater complexity are commonly used (e.g. suchas a 2-bit full-adder or muxed D-input flip-flop).

As illustrated in FIG. 1, the array of standard cells may be arranged inrows, with each row including a plurality of standard cells. Each rowextends in a first direction (e.g. an x-direction). Each standard cellis defined by a cell boundary, and adjacent standard cells in a givenrow may have cell boundaries that abut each other. Additionally, asshown in FIG. 1, standard cells in adjacent rows may have cellboundaries that abut each other. As mentioned above, each standard cellmay include a group of transistors and interconnect structures thatimplement a circuit (e.g. providing a Boolean logic function or astorage function). To implement such functionality, each of the standardcells may include complementary metal-oxide-semiconductor field-effecttransistors (CMOSFETs). For example, each of the standard cells mayinclude one or more P-type MOSFETs (PMOSFETs) formed in an N-type wellregion and one or more N-type MOSFETs (NMOSFETs) formed in a P-type wellregion. The N-type well regions, the P-type well regions, and theboundaries therebetween are shown in FIG. 1. In an embodiment, each ofthe one or more PMOSFETs and the one or more NMOSFETs of a standard cellmay be implemented using a fin-like field-effect transistor (FinFET)device. However, it is noted that other types of transistor devices maybe used, examples being gate-all-around (GAA) transistor devices andplanar transistor devices.

As shown in FIG. 1, a row of the array of standard cells (e.g. Row i ofFIG. 1) includes a first standard cell SC1 and a second standard cellSC2, which are adjacent to each other (e.g. immediately adjacent to eachother) in the first direction (e.g. the x-direction). The Row i isadjacent to Row i+1 and Row i−1 in a second direction (e.g. ay-direction). The second direction may be substantially perpendicular tothe first direction. The Row i+1 includes a third standard cell SC3 anda fourth standard cell SC4, which are adjacent to each other in thefirst direction. Similarly, the Row i−1 includes a fifth standard cellSC5 and a sixth standard cell SC6, which are adjacent to each other inthe first direction.

Each of the standard cells SC1, SC2, SC3, SC4, SC5, and SC6 may includeone or more multiple-fin FinFET devices, one or more single-fin FinFETdevices, or a combination thereof. A multiple-fin FinFET device may be aFinFET device that includes two or more semiconductor fins, where a gatestructure (that is common to the two or more semiconductor fins)controls current flow in channel regions of the two or moresemiconductor fins. On the other hand, a single-fin FinFET device may bea FinFET device that includes no more than one semiconductor fin, wherea gate structure engages the one semiconductor fin and controls currentflow in a channel region of the one semiconductor fin. Multiple-finFinFET devices may be used for high speed applications, while single-finFinFET devices may be used for low leakage and low power (e.g. lowactive power and/or low standby power) applications. Consequently, anintegrated circuit device 100 having multiple-fin FinFET devices andsingle-fin FinFET devices may be used for both high performance and lowleakage applications, particularly for SoC products.

Standard cells of the array of standard cells may have a respectivedimension. For example, in the embodiment of FIG. 1, each standard cellof the Row i may have a dimension H_(i), each standard cell of the Rowi−1 may have a dimension and each standard cell of the Row i+1 may havea dimension H_(i+1). The dimensions H_(i), and H_(i+1), which aremeasured in the second direction, may correspond to the cell heights ofthe standard cells of Row i, Row i−1, and Row i+1, respectively. In someembodiments, the dimensions H_(i), and H_(i+1) may be in a range of fromabout 50 nm to about 100 nm.

In some embodiments, such as in the example of FIG. 1, the integratedcircuit device 100 may also include a plurality of filler cells. Theplurality of filler cells may include dummy cells lacking functionalityor circuitry. Additionally or alternatively, the plurality of fillercells may include a well tap cell for biasing the N-type well regionand/or P-type well region over which the well tap cell is disposed, withsuch a well tap cell including well strap structures (e.g. implementedusing a plurality of fin structures).

Each of the standard cells of the integrated circuit device 100 mayinclude interconnect structures that are coupled together to implement agiven circuit (e.g. providing a Boolean logic function or a storagefunction). Such interconnect structures of a standard cell may includemid-end-of-line (MEOL) interconnect structures, examples being draincontacts, source contacts, and gate contacts, each of which may bedisposed or formed in a dielectric layer (e.g. an inter-layer dielectriclayer, often abbreviated as an “ILD layer”). In such examples, the draincontacts, source contacts, and gate contacts may respectively land onand contact (e.g. electrically and/or physically contact) drainfeatures, source features, and gate structures of the FinFET devices ofthe standard cell.

However, as technology progresses towards smaller technology nodes (e.g.32 nm, 28 nm, 20 nm, and smaller), there is a corresponding decrease inthe dimensions of the standard cells of the integrated circuit device100. As an example, the cell heights H_(i), and H_(i+1) of the standardcells of Row i, Row i−1, and Row i+1 may decrease, and this may resultin a corresponding decrease in the dimensions of the interconnectstructures of the standard cells. Additionally, a distance betweeninterconnect structures of adjacent standard cells may decrease. Forexample, the fifth standard cell SC5 is adjacent to the first standardcell SC1 in the second direction, and a distance between a drain contactof the fifth standard cell SC5 and a source contact of the firststandard cell SC1 may decrease in tandem with progressively smaller cellheights. Although resulting in greater integration and more efficientuse of chip real estate, several challenges accompany the decrease infeature size and the decrease in distance between interconnectstructures of adjacent standard cells. For example, in some instances, adrain contact of one standard cell (e.g. the fifth standard cell SC5)may be adjacent to a source contact of another standard cell (e.g. thefirst standard cell SC1) in the second direction. A typical lithographyand etching process used to form these contacts may include initiallyforming a single continuous conductive structure in an opening andsubsequently etching, cutting, or removing a central portion of thesingle continuous conductive structure, thereby resulting in twoseparate conductive structures. In this example, the two separateconductive structures formed by such a process are the drain contact ofthe one standard cell (e.g. the fifth standard cell SC5) and the sourcecontact of the adjacent standard cell (e.g. the first standard cellSC1). Such a typical lithography and etching process relies on an etchmask having a cut window with a critical dimension that is less than orequal to the distance separating the adjacent contacts in the seconddirection. However, as the dimensions of the standard cells of theintegrated circuit device 100 decrease, such critical dimensions for thecut window may be difficult to attain, and this may increase thepossibility of failure in the lithography and etching process.Additionally, for an integrated circuit device that includes a pluralityof standard cells, there may be a plurality of cut windows that areneeded to form the source and drain contacts for each of the standardcells of the integrated circuit device. This, in turn, increases thecomplexity of the typical lithography and etching process. Furthermore,a decrease in the distance between the adjacent contacts also results inan increase in parasitic capacitances due, at least in part, to thecloser proximity of the drain contact of the one standard cell (e.g. thefifth standard cell SC5) and the source contact of the adjacent standardcell (e.g. the first standard cell SC1). Even further, a decrease infeature size results in an increase in the contact resistance of thesource and drain contacts.

The present disclosure aims to circumvent the above-described drawbacksthat accompany the decrease in feature size. In particular, the presentdisclosure proposes structural features for the source contacts of thestandard cells of the integrated circuit device 100 that result in adecrease in parasitic capacitance between a source contact and anadjacent drain contact, even as technology progresses towards smallertechnology nodes. The structural features of the source contacts of thestandard cells of the integrated circuit device 100 also lead to adecrease in a contact resistance between a respective source contact anda respective power supply line to which the respective source contact iscoupled. The decrease in parasitic capacitance and the decrease incontact resistance also lead to an increase in an operating speed of thestandard cells of the integrated circuit device 100. Furthermore, thepresent disclosure presents one or more embodiment methods that may beused to form the embodiment source contacts. The one or more embodimentmethods have less constrained critical dimension requirements andprocess windows requirements in comparison to the typical lithographyand etching process described above.

In order to highlight the structural features of the source contactsproposed in this disclosure, reference is first made to FIG. 2, whichshows a simplified top-down schematic view of the standard cells SC1,SC3, and SC5 shown in FIG. 1, in accordance with an embodiment. FIG. 2illustrates the cell boundaries of the first, third, and fifth standardcells SC1, SC3, and SC5. In the example of FIG. 2, the cell boundariesof the first, third, and fifth standard cells SC1, SC3, and SC5 areshown as being aligned along the second direction for the sake ofsimplicity and clarity. However, in other embodiments, the boundaries ofthe first, third, and fifth standard cells SC1, SC3, and SC5 may not bealigned to one another along the second direction. As discussed above,standard cells of the integrated circuit device 100 include CMOSFETs,which may be implemented using FinFET devices. Consequently, as seen inFIG. 2, the first standard cell SC1 includes fin structures 102 a, 102 bthat are oriented or routed along the first direction (e.g. thex-direction). Stated differently, the fin structures 102 a, 102 b extendlongitudinally or lengthwise along the first direction. The longitudinalaxes of the fin structures 102 a, 102 b may, as an example, be in adirection of a current flow between source/drain features of the finstructures 102 a, 102 b, respectively. In some embodiments, the adjacentfin structures 102 a, 102 b of the first standard cell SC1 may beseparated from each other in the second direction by a distance D1,which may be in a range from about 10 nm to about 200 nm.

The fin structure 102 a of the first standard cell SC1 may be formed inthe P-type well region, while the fin structure 102 b of the firststandard cell SC1 may be formed in the N-type well region. The finstructure 102 a may have an N-type conductivity, and the fin structure102 b may have a P-type conductivity. Consequently, the fin structures102 a and 102 b may be active fin structures or device fin structuresused to implement an NMOSFET device (e.g. a single-fin N-type FinFETdevice) and a PMOSFET device (e.g. a single-fin P-type FinFET device),respectively. To implement such transistor devices, the first standardcell SC1 includes active gate structures, each of which engages the finstructures 102 a, 102 b at channel regions thereof. An active gatestructure generally refers to an electrically functional gate structureof a transistor device that is used to enable or control current flowbetween source and drain regions of the transistor device. Each activegate structure of the first standard cell SC1 extends longitudinally orlengthwise along the second direction (e.g. the y-direction). Stateddifferently, a longitudinal axis of the each of the active gatestructures may be oriented along the second direction, while atransverse axis of the active gate structures may be oriented along thefirst direction. It is noted that the transverse axes of the finstructures 102 a, 102 b may be oriented along the second direction.

FIG. 2 also shows drain contacts that land on and contact (e.g.electrically and/or physically contact) drain features of the finstructures 102 a, 102 b. As shown in FIG. 2, some drain contacts of thefirst standard cell SC1 contact the fin structure 102 a, but not the finstructure 102 b. Other drain contacts of the first standard cell SC1contact the fin structure 102 b, but not the fin structure 102 a. Yetother drain contacts of the first standard cell SC1 contact both finstructures 102 a and 102 b. In general, the fin structures 102 a, 102 bon which the drain contacts land may depend on design requirements ofthe integrated circuit device 100 and on the specific circuitimplemented by the first standard cell SC1. The drain contacts arecoupled to one or more overlying metallization layers (e.g. M₀ to M_(z))by via structures that land on and contact (e.g. electrically and/orphysically contact) the drain contacts of the first standard cell SC1.The one or more overlying metallization layers are not shown in FIG. 2for the sake of simplicity and clarity.

The integrated circuit device 100 includes power supply lines 101 a to101 d that extend longitudinally or lengthwise along the first direction(e.g. the x-direction). The power supply lines 101 a to 101 d may beparallel to the fin structures 102 a, 102 b. Each of the power supplylines 101 a to 101 d supplies a respective bias voltage (e.g. Vdd orVss) to the FinFET devices of the integrated circuit device 101. Forexample, with regards to the first standard cell SC1, FIG. 2 showssource contacts that couple source features of the fin structure 102 ato the power supply line 101 b (e.g. having a bias voltage Vss). FIG. 2also shows source contacts that couple source features of the finstructure 102 b to the power supply line 101 c (e.g. having a biasvoltage Vdd). The bias voltage Vss may be configured as ground and/or anegative supply voltage, depending on design requirements, while thebias voltage Vdd may be configured as a positive supply voltage,depending on design requirements.

FIG. 2 also shows isolation structures that are disposed on theboundaries of the first standard cell SC1. The isolation structures ofthe first standard cell SC1 isolate the first and second standard cellsSC1, SC2 from each other and from other standard cells of the Row i. Theisolation structures may include a dielectric material such as siliconoxide or silicon nitride, as examples. In the example of FIG. 2, theisolation structures are implemented using dielectric gate structures(also referred to as dummy gate structures). A dummy gate structuregenerally refers to an electrically non-functioning gate structure of atransistor device. In some embodiments, such as in the example of FIG.2, the dummy gate structures mimic physical properties of the activegate structures, such as physical dimensions of the active gatestructures, but are electrically inoperable and do not enable current toflow between source and drain regions of a transistor device. It is alsonoted that the dummy gate structures and the active gate structures havethe same routing direction (e.g. in the y-direction).

The features described above in reference to the first standard cell SC1are also observed in the third standard cell SC3 and the fifth standardcell SC5 shown in FIG. 2. For example, the third standard cell SC3includes fin structures 104 a, 104 b that are oriented or routed alongthe first direction. Adjacent fin structures 104 a, 104 b of the thirdstandard cell SC3 may be separated from each other, in the seconddirection, by a distance D2, which may be in a similar range of valuesas described above in reference to the distance D1. The fin structure104 a of the third standard cell SC3 may be formed in the N-type wellregion, while the fin structure 104 b of the third standard cell SC3 maybe formed in the P-type well region. The fin structure 104 a may have aP-type conductivity, and the fin structure 104 b may have an N-typeconductivity. Consequently, the fin structures 104 a and 104 b may beactive fin structures or device fin structures used to implement aPMOSFET device and an NMOSFET device, respectively. The third standardcell SC3 includes active gate structures, each of which engages the finstructures 104 a, 104 b at channel regions thereof. FIG. 2 also showsdrain contacts that land on and contact (e.g. electrically and/orphysically contact) drain features of the fin structures 104 a, 104 b ofthe third standard cell SC3. The drain contacts are coupled to one ormore overlying metallization layers by via structures that land on andcontact (e.g. electrically and/or physically contact) the drain contactsof the third standard cell SC3. Additionally, source contacts couplesource features of the fin structures 104 a, 104 b to the power supplylines 101 c, 101 d, respectively. Isolation structures are disposed onthe boundaries of the third standard cell SC3. The isolation structuresof the third standard cell SC3 isolate the third and fourth standardcells SC3, SC4 from each other and from other standard cells of the Rowi+1.

Similarly, the fifth standard cell SC5 includes fin structures 106 a,106 b that are oriented or routed along the first direction. Adjacentfin structures 106 a, 106 b of the fifth standard cell SC5 may beseparated from each other, in the second direction, by a distance D3,which may be in a similar range of values as described above inreference to the distance D1. The fin structure 106 a of the fifthstandard cell SC5 may be formed in the N-type well region, while the finstructure 106 b of the fifth standard cell SC5 may be formed in theP-type well region. The fin structure 106 a may have a P-typeconductivity, and the fin structure 106 b may have an N-typeconductivity. Consequently, the fin structures 106 a and 106 b may beactive fin structures or device fin structures used to implement aPMOSFET device and an NMOSFET device, respectively. The fifth standardcell SC5 includes active gate structures, each of which engages the finstructures 106 a, 106 b at channel regions thereof. FIG. 2 also showsdrain contacts that land on and contact (e.g. electrically and/orphysically contact) drain features of the fin structures 106 a, 106 b ofthe fifth standard cell SC5. The drain contacts are coupled to one ormore overlying metallization layers by via structures that land on andcontact (e.g. electrically and/or physically contact) the drain contactsof the fifth standard cell SC5. Additionally, source contacts couplesource features of the fin structures 106 a, 106 b to the power supplylines 101 a, 101 b, respectively. Isolation structures are disposed onthe boundaries of the fifth standard cell SC5 to isolate the fifth andsixth standard cells SC5, SC6 from each other and from other standardcells of the Row i−1.

FIG. 2 illustrates a region 200 of the integrated circuit device 100.FIG. 3 shows a zoomed-in view of the region 200, in accordance with anembodiment. It is noted that while the following description is directedto the region 200 of the integrated circuit device 100, the featuresdescribed below apply analogously to other regions of the integratedcircuit device 100 having a similar structure and layout as the region200.

FIG. 3 shows an active gate structure 302-1 of the first standard cellSC1 and an active gate structure 302-2 of the fifth standard cell SC5.The active gate structure 302-1 of the first standard cell SC1 includesa gate stack 304-1 and a gate spacer 306-1 disposed along sidewalls ofthe gate stack 304-1. The active gate structure 302-2 of the fifthstandard cell SC5 includes a gate stack 304-2 and a gate spacer 306-2disposed along sidewalls of the gate stack 304-2. The gate stack 304-1of the active gate structure 302-1 may include a gate dielectric layer,a barrier layer, a seed layer, and a gate electrode. For example, thegate dielectric layer may contact (e.g. physically contact) a channelregion of the fin structure 102 a and may include silicon oxide, siliconnitride, or a high-k dielectric material (e.g. k>7.0) including a metaloxide or a silicate of Hf, Al, Zr, La, Mg, Y, Sr, Ba, Ti, Pb, or acombination thereof. As an example, the gate dielectric layer mayinclude hafnium oxide (HfO₂), zirconium oxide (ZrO₂), lanthanum oxide(La₂O₃), titanium oxide (TiO₂), yttrium oxide (Y₂O₃), strontium titanate(SrTiO₃). The gate dielectric layer may, as an example, be formed usingmolecular beam deposition (MBD), atomic layer deposition (ALD),plasma-enhanced CVD (PECVD), and the like. The barrier layer of the gatestack 304-1 may include an electrically conductive material such astitanium nitride, although other materials, such as tantalum nitride,titanium, tantalum, or the like, may alternatively be utilized. Thebarrier layer may be formed using a CVD process, such as PECVD. Workfunction layers may be included in the gate stack 304-1. For example,P-type work function layer(s) may be formed in regions of the gate stack304-1 that are used to implement a PMOSFET device, and N-type workfunction layer(s) may be formed in regions of the gate stack 304-1 thatare used to implement an NMOSFET device. The P-type work function layermay include TiN, TaN, Ru, Mo, Al, WN, ZrSi₂, MoSi₂, TaSi₂, NiSi₂, WN,other suitable P-type work function materials, or a combination thereof.The N-type work function layer may include Ti, Ag, TaAl, TaAlC, TiAlN,TaC, TaCN, TaSiN, Mn, Zr, other suitable N-type work function materials,or a combination thereof. The seed layer of the gate stack 304-1 isformed over the barrier layer (or the work function layers, if present).The seed layer may include Cu, Ti, Ta, TiN, TaN, the like, or acombination thereof, and may be deposited by ALD, sputtering, physicalvapor deposition (PVD), or the like. The gate electrode of the gatestack 304-1 may include a metal-containing material such as TiN, TaN,TaC, Co, Ru, Al, combinations thereof, or multi-layers thereof, and maybe formed by, e.g., electroplating, electroless plating, or othersuitable method. The gate stack 304-2 of the active gate structure 302-2may be similar to the gate stack 304-1 of the active gate structure302-1 in structure and in composition. Consequently, the descriptionprovided above in reference to the gate stack 304-1 applies analogouslyto the gate stack 304-2.

The gate spacers 306-1 of the active gate structure 302-1 may be asingle layer or a multi-layer structure. In an embodiment, the gatespacers 306-1 include a low-k (e.g. k<7.0) dielectric material. The gatespacers 306-1 may include an oxide of silicon (e.g. SiO₂), a nitride ofsilicon (e.g. Si₃N₄), another dielectric material (e.g. silicon carbide,silicon carbonitride), or combination thereof (e.g. silicon oxynitride).The gate spacers 306-2 of the active gate structure 302-2 may be similarto the gate spacers 306-1 of the active gate structure 302-1 instructure and in composition. Consequently, the description providedabove in reference to the gate spacers 306-1 applies analogously to thegate spacers 306-2. The isolation structures of the first and fifthstandard cell SC1, SC5 may include a dielectric material 308, such assilicon oxide or silicon nitride. As illustrated in FIG. 3, gate spacers306-1 and 306-2 are also disposed along sidewalls of the dielectricmaterial 308 in the first standard cell SC1 and the fifth standard cellSC5, respectively.

The fifth standard cell SC5 includes drain contact 310 and sourcecontact 312, while the first standard cell SC1 includes source contact314 and drain contact 316. As seen in FIG. 3, the via structure 318 isdisposed on the drain contact 310 of the fifth standard cell SC5. Insome embodiments, a first dimension W1 of each of the source contacts312, 314 (e.g. measured in the first direction) may be in a range fromabout 6 nanometers to about 30 nanometers, while a second dimension W2of each of the source contacts 312, 314 (e.g. measured in the seconddirection) may be in a range from about 10 nanometers to about 300nanometers. In some embodiments, a ratio of the dimension W2 to thedimension W1 may be in a range from about 1 to about 50.

As technology progresses towards smaller technology nodes (e.g. 32 nm,28 nm, 20 nm, and smaller), there is a corresponding decrease in adistance D4 that separates the drain contact 310 of the fifth standardcell SC5 and the source contact 314 of the first standard cell SC1, asmeasured in the second direction. In like manner, there is also acorresponding decrease in a distance D5 that separates the sourcecontact 312 of the fifth standard cell SC5 and the drain contact 316 ofthe first standard cell SC1, as measured in the second direction. Insome embodiments, the distances D4 and D5 may be in a range from about 5nm to about 100 nm.

FIG. 3 illustrates a line A-A along which a cross-sectional view of thefirst standard cell SC1 and the fifth standard cell SC5 are taken. Thecross-sectional view along the line A-A is shown in FIG. 4, which showsa cross-sectional view of the transistor devices of FIG. 3, inaccordance with an embodiment. The integrated circuit device 100includes a substrate 402. The substrate 402 may be a semiconductorsubstrate, such as a bulk semiconductor, a semiconductor-on-insulator(SOI) substrate, or the like, which may be doped (e.g. with a P-type oran N-type dopant) or undoped. The substrate 402 may be a wafer, such asa silicon wafer. Generally, an SOI substrate includes a layer of asemiconductor material formed on an insulator layer. The insulator layermay be, for example, a buried oxide (BOX) layer, a silicon oxide layer,or the like. The insulator layer is provided on a substrate, typically asilicon or glass substrate. Other substrates, such as a multi-layered orgradient substrate may also be used. The semiconductor material of thesubstrate 402 may include silicon; germanium; a compound semiconductorincluding silicon carbide, gallium arsenic, gallium phosphide, indiumphosphide, indium arsenide, and/or indium antimonide; an alloysemiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP,and/or GaInAsP; or a combination thereof.

The substrate 402 includes various doped regions configured according todesign requirements of the integrated circuit device 100. For example,the substrate 402 may include P-type doped regions (for example, P-typewells) doped with P-type dopants, such as boron (for example, BF₂),indium, other P-type dopants, or combinations thereof. Additionally oralternatively, the substrate 402 may include N-type doped regions (forexample, N-type wells) doped with N-type dopants, such as phosphorus,arsenic, other N-type dopants, or combinations thereof. The variousdoped regions can be formed directly on and/or in the substrate 402, forexample, providing P-type well regions and N-type well regions (e.g.shown in FIGS. 1 and 2). An ion implantation process, a diffusionprocess, or other suitable doping process can be performed eitherindividually or in combination to form the P-type well regions andN-type well regions. In the embodiment of FIG. 4, the P-type well regionthat is shared by the first standard cell SC1 and the fifth standardcell SC5 is depicted as P-type well region 404. In some embodiments, theP-type well regions of the integrated circuit device 100 have a P-typedopant concentration of about 1×10¹⁶ cm⁻³ to about 1×10¹⁹ cm³, while theN-type well regions of the integrated circuit device 100 have an N-typedopant concentration of about 1×10¹⁶ cm⁻³ to about 1×10¹⁹ cm³.

As illustrated in FIG. 4, the fin structures 102 a and 106 b protrudeout of the P-type well region 404. For example, the fin structures 102 aand 106 b protrude from a major surface 404 a of the P-type well region404 in a third direction (e.g. a z-direction). The third direction issubstantially perpendicular to the first direction and the seconddirection. The major surface 404 a of the P-type well region 404 mayrefer to the planar surface of the P-type well region 404 that lies inan x-y plane. As discussed above in reference to FIG. 2, the finstructures 102 a and 106 b are used to implement NMOSFETs and may havean N-type conductivity. As such, the fin structures of the integratedcircuit device 100 having an N-type conductivity (e.g. fin structures102 a, 106 b, 104 b) may have an N-type dopant concentration of about1×10¹⁶ cm³ to about 1×10¹⁹ cm⁻³. It is also noted that fin structures ofthe integrated circuit device 100 having a P-type conductivity (e.g. finstructures 102 b, 104 a, 106 a) may have a P-type dopant concentrationof about 1×10¹⁶ cm⁻³ to about 1×10¹⁹ cm³.

A first dielectric layer 406 conformally lines the major surface 404 aof the P-type well region 404 and the sidewalls SW₁ of the finstructures 102 a and 106 b. The first dielectric layer 106 may be anisolation feature, such as a shallow trench isolation feature (STI). Thefirst dielectric layer 406 may include a single dielectric materiallayer or multiple dielectric material layers. Suitable dielectricmaterials for the first dielectric layer 404 include silicon oxides,silicon nitrides, silicon carbides, fluoro-silicate glass (FSG), low-Kdielectric materials, other suitable dielectric materials, or acombination thereof. In the example of FIG. 4, the fin structures 102 aand 106 b extend out of the first dielectric layer 406 in the thirddirection. However, in other embodiments, the portions of the firstdielectric layer 406 lining the fin structures 102 a, 106 b have topsurfaces that are substantially co-planar with top surfaces of the finstructures 102 a and 106 b.

An epitaxial source feature 408 may be formed on a source region of thefin structure 102 a, while an epitaxial drain feature 410 may be formedon a drain region of the fin structure 106 b. In the example of FIG. 4,the epitaxial source feature 408 and the epitaxial drain feature 410 areN-type features including silicon, silicon carbide (SiC), siliconphosphorous (SiP), phosphorous-doped silicon carbon (SiCP), the like, ora combination thereof. In some embodiments, the epitaxial source feature408 and the epitaxial drain feature 410 may have an N-type dopantconcentration of about 5×10¹⁹ cm⁻³ to about 1×10²² cm³. It is noted thatP-type epitaxial source/drain features of the integrated circuit device100 (e.g. the source/drain features of fin structures 102 b, 104 a, 106a) may include silicon, germanium, silicon germanium (SiGe), silicongermanium carbon (SiGeC), or a combination thereof as well as a P-typeimpurity such as boron or indium. Such P-type epitaxial source/drainfeatures of the integrated circuit device 100 may have a P-type dopantconcentration of about 1×10¹⁹ cm³ to about 6×10²¹ cm⁻³ In the embodimentof FIG. 4, where the fin structures 102 a, 106 b extend out of the firstdielectric layer 406, the epitaxial source feature 408 wraps the sourceregion of the fin structure 102 a, while the epitaxial drain feature 410wraps the drain region of the fin structure 106 b.

The power supply line 101 b is disposed in a trench that is defined bythe first dielectric layer 406. Stated differently, the power supplyline 101 b may be buried in an insulating layer and may be laterallyadjacent to transistor features. The power supply line 101 b may, as anexample, define a boundary between the first standard cell SC1 and thefifth standard cell SC5 and may be laterally adjacent to the finstructure 102 a and to the fin structure 106 b in the second direction.The power supply line 101 b may include a barrier layer 412, a seedlayer 414, and a conductive material 416. The barrier layer 412 mayinclude an electrically conductive material such as Ti, TiN, Ta, TaN, orthe like. The seed layer 414 may be formed of tungsten, copper, orcopper alloys. The conductive material 416 may include tungsten,although other suitable materials such as aluminum, copper, tungstennitride, platinum, ruthenium, silver, gold, rhodium, molybdenum, nickel,cobalt, cadmium, zinc, alloys of these, combinations thereof, and thelike, may alternatively be utilized.

As shown in FIG. 4, the integrated circuit 100 may include fill fins 418a, 418 b, 418 c that extend out of the first dielectric layer 406 in thethird direction. In other words, the fill fins 418 a, 418 b, 418 cextend upwardly from trenches defined by the conformal first dielectriclayer 406. Like the fins structures 102 a, 106 b, the fill fins 418 a,418 b, 418 c extend longitudinally or lengthwise in the first direction.The fill fins 418 a, 418 b, 418 c are dielectric features filling aspace between adjacent fin structures of the integrated circuit device100 (e.g. the fin structures 102 a, 106 b) and may tune overall finpattern density, reinforce the mechanical strength of the fin structuresof the integrated circuit device 100, and enhance the manufacturingcapability. The epitaxial drain feature 410 may be located in a spacebetween adjacent fill fins 418 b, 418 c in the second direction, asillustrated in FIG. 4. Consequently, as discussed below in reference tothe method shown in FIGS. 6A to 6Q, the adjacent fill fins 418 b, 418 cmay be used to self-align the epitaxial drain feature 410 to the drainregion of the fin structure 106 b.

The dielectric material of the fill fins 418 may be different from thatof the first dielectric layer 406 (e.g. to achieve etching selectivity).For example, the dielectric material of the fill fins 418 may be ahigh-k dielectric material, such as a metal oxide, examples beinghafnium oxide (HfO₂), zirconium oxide (ZrO₂), aluminum oxide (Al₂O₃), orthe like. As another example, the dielectric material of the fill fins418 may include a carbon-containing dielectric material, such as siliconcarbon oxide, silicon carbon oxynitride, silicon carbon nitride, or acombination thereof.

FIG. 4 also shows a second dielectric layer 420, which acts as aninsulator that supports and isolates conductive traces (such ascontacts, vias and metal lines) to be formed therein. The seconddielectric layer 420 may be an ILD layer and may include any suitabledielectric material, such as a silicon oxide, low-k dielectric material,porous dielectric material, other suitable dielectric material, or acombination thereof. As examples, the second dielectric layer 420 mayinclude silicon oxide, doped silicon oxide such as borophosphosilicateglass (BPSG), tetraethylorthosilicate (TEOS) oxide, un-doped silicateglass, fused silica glass (FSG), phosphosilicate glass (PSG), borondoped silicon glass (BSG), silicon nitride, silicon oxynitride, siliconcarbide, low-k dielectric material, other suitable materials, orcombinations thereof.

The drain contact 310 is disposed in the second dielectric layer 420 andcontacts (e.g. physically contacts) the epitaxial drain feature 410.Stated differently, the drain contact 310 is encapsulated in the seconddielectric layer 410, and a portion of the drain contact 310 contacts(e.g. physically contacts) one or more upward-facing surfaces of theepitaxial drain feature 410. The drain contact 310 may include anysuitable electrically conductive material, such as Ta, Ti, Al, Ni, Mo,Pt, Ru, Cu, Co, W, TiN, TaN, other suitable conductive materials, orcombinations thereof. The portion of the drain contact 310 that contactsthe epitaxial drain feature 410 is located in the space between adjacentfill fins 418 b, 418 c in the second direction. As such, the adjacentfill fins 418 b, 418 c may also serve to self-align the drain contact310 to the epitaxial drain feature 410 (this is discussed below inreference to the method shown in FIGS. 6A to 6Q). In some embodiments,such as in the example of FIG. 4, a drain silicide layer 422 is disposedbetween the one or more upward-facing surfaces of the epitaxial drainfeature 410 and the drain contact 310. The drain silicide layer 422 mayinclude a material of the epitaxial drain feature 410 and a silicide ofnickel, platinum, palladium, vanadium, titanium, cobalt, tantalum,ytterbium, zirconium, other suitable metal, or combinations thereof.

As seen in FIG. 4, the source contact 314 includes a lateral component314 a (also referred to as a lateral portion) that extends in the seconddirection (e.g. the y-direction). The lateral component 314 a contacts(e.g. physically contacts) one or more upward-facing surfaces of theepitaxial source region 408. The source contact 314 also includes avertical component 314 b (also referred to as a vertical portion) thatextends in the third direction (e.g. the z-direction) towards the powersupply line 101 b. A surface 314 c of the vertical component 314 bdirected towards the power supply line 101 b (e.g. the bottom surface ofthe vertical component 314 b) may physically contact the power supplyline 101 b. As a result of the physical contact made between the sourcecontact 314 and the power supply line 101 b, the epitaxial sourcefeature 408 may be biased at a voltage that is substantially equal tothe voltage carried by the power supply line 101 b.

In some examples, a dimension D6 of the surface 314 c of the verticalcomponent 314 b that is in contact with the power supply line 101 b, asmeasured in the second direction, may be greater than about 12nanometers (e.g. in a range from about 8 nm to about 30 nm. When thedimension D6 is in the above-stated range of values, the contact areamade between the surface 314 c of the vertical component 314 b and thepower supply line 101 b is maximized, while keeping the source contact314 within the boundary of the first standard cell SC1. As a result,contact resistance between the source contact 314 and the power supplyline 101 b is minimized, which in turn increases an operating speed ofthe first standard cell SC1 by at least 0.5% (e.g. in a range from about0.5% to about 10%).

FIGS. 5A and 5B shows a zoomed-in view of the source contact 314 and thepower supply line 101 b, in accordance with an embodiment. As seen inFIG. 5A, the source contact 314 may include a barrier layer 502, a seedlayer 504, and a conductive material 506. The barrier layer 502 may beinclude one or more materials described above in reference to thebarrier layer 412 of the power supply line 101 b. The seed layer 504 mayinclude one or more materials described above in reference to the seedlayer 414 of the power supply line 101 b. The conductive material 506may include one or more materials described above in reference to theconductive material 416 of the power supply line 101 b.

In the example of FIG. 4, a sidewall SW₂ of the vertical component 314 bmay be aligned with a sidewall SW₃ of the power supply line 101 b. Insome embodiments, such as in the example of FIG. 4, a source silicidelayer 424 is disposed between the epitaxial source feature 408 and thesource contact 314. The source silicide layer 424 may include a materialof the epitaxial source feature 408 and a silicide of nickel, platinum,palladium, vanadium, titanium, cobalt, tantalum, ytterbium, zirconium,other suitable metal, or combinations thereof. An etch stop layer 426may be disposed over the second dielectric layer 420 and over a surface314 d of the source contact 314 directed away from the substrate 402.The etch stop layer 426 may include a dielectric material such assilicon nitride (Si₃N₄), silicon oxide (SiO₂), silicon oxynitride(SiON), and/or other materials. The via structure 318 is disposed in theetch stop layer 416. The via structure 318 may include one or more ofthe materials described above in reference to the drain contact 310.

As seen in the example of FIG. 4, the surface 314 d of the sourcecontact 314 directed away from the substrate 402 is recessed incomparison with a surface 310 a of the drain contact 310 directed awayfrom the substrate 402. In such embodiments, this offset between thesurfaces 314 d and 310 a may result in a decrease in an area of overlapbetween sidewall surfaces of the drain contact 310 and the sourcecontact 314 that face each other. This decrease in the area of overlapresults in a corresponding decrease in a parasitic capacitance betweenthe drain contact 310 and the source contact 314 (e.g. in comparisonwith typical source and drain contacts that are formed in an ILD layer,where each of the typical source and drain contacts is coupled to anoverlying metallization layer by a respective via structure). This, inturn, increases an operating speed of the first standard cell SC1 andthe fifth standard cell SC5 by at least 0.1% (e.g. in a range of 0.1%and 5%).

FIGS. 6A to 6Q illustrate a method of forming the features shown in FIG.4, in accordance with an embodiment. FIG. 6A shows fin structures 102 a,106 b (having an N-type conductivity) protruding from the major surface404 a of the P-type well region 404 in the third direction. The P-typewell region 404 and fin structures 102 a, 106 b may be formed by anysuitable process. For example, in some embodiments, a combination ofdeposition, lithography, etching, and/or implantation processes areperformed to define these features. Similar processes may be used toform the N-type well regions, the fin structures 102 b, 104 a, 104 b,106 a, and the other P-type well regions shown in FIG. 2. For example,an embodiment process for forming the P-type well regions, N-type wellregions, and fin structures includes forming trenches in the substrate402 to define semiconductor strips, and subsequently performing aplurality of doping processes to define the P-type well regions, theN-type well regions, the fin structures 106 b, 102 a, and 104 b in theP-type well regions, and the fin structures 106 a, 102 b, 104 a in theN-type well regions. As an example, the lithography process used to formtrenches in the substrate 402 can include forming a resist layer on thesubstrate 402 (for example, by spin coating), performing a pre-exposurebaking process, performing an exposure process using a mask, performinga post-exposure baking process, and performing a developing process.During the exposure process, the resist layer is exposed to radiationenergy (for example, ultraviolet (UV) light, deep UV (DUV) light, orextreme UV (EUV) light). The mask blocks, transmits, and/or reflectsradiation to the resist layer depending on a mask pattern of the maskand/or mask type (for example, binary mask, phase shift mask, or EUVmask), such that an image is projected onto the resist layer thatcorresponds with the mask pattern. Since the resist layer is sensitiveto radiation energy, exposed portions of the resist layer chemicallychange, and exposed (or non-exposed) portions of the resist layer aredissolved during the developing process depending on characteristics ofthe resist layer and characteristics of a developing solution used inthe developing process. After development, the patterned resist layerincludes a resist pattern that corresponds with the mask.

The etching process that follows the lithography process uses thepatterned resist layer as an etch mask to remove portions of thesubstrate 402 that are exposed. The etching process can include a dryetching process (for example, an RIE process), a wet etching process,other suitable etching process, or combinations thereof. After theetching process, the patterned resist layer is removed from thesubstrate 402, for example, by a resist stripping process, therebydefining semiconductor strips extending out of the substrate 402.

The above-described process of forming the semiconductor strips andtrenches in the substrate 402 is one of other suitable processes. Forexample, in other embodiments, the semiconductor strips may be formedfrom the substrate 402 by a multiple patterning process, such as adouble patterning lithography (DPL) process (for example, alithography-etch-lithography-etch (LELE) process, a self-aligned doublepatterning (SADP) process, a spacer-is-dielectric (SID) SADP process,other double patterning process, or combinations thereof), a triplepatterning process (for example, alithography-etch-lithography-etch-lithography-etch (LELELE) process, aself-aligned triple patterning (SATP) process, other triple patterningprocess, or combinations thereof), other multiple patterning process(for example, self-aligned quadruple patterning (SAQP) process), orcombinations thereof. Additionally or alternatively, directedself-assembly (DSA) techniques are implemented while forming thesemiconductor strips from the substrate 402. Further, in someembodiments, the exposure process can implement maskless lithography,electron-beam (e-beam) writing, ion-beam writing, and/or nanoimprinttechnology for patterning the resist layer and/or other layers.

Subsequent to forming the semiconductor strips in the substrate 402, theplurality of doping processes are performed to appropriately doperegions of the substrate 402 and the semiconductor strips to define theP-type well regions, the N-type well regions, the fin structures 106 b,102 a, and 104 b in the P-type well regions, and the fin structures 106a, 102 b, 104 a in the N-type well regions. The plurality of dopingprocess may include an ion implantation process and/or a diffusionprocess.

Referring to FIG. 6B, the first dielectric layer 406 is deposited on themajor surface 404 a of the P-type well region 404 with a conformalprofile, covering the fin structures 102 a, 106 b. The first dielectriclayer 406 may be deposited by any suitable technique including thermalgrowth, CVD, high-density plasma CVD (HDP-CVD), PVD, ALD, and/or spin-ontechniques. As a result of the conformal profile of the first dielectriclayer 406, trenches 602 a, 602 b, 602 c are defined by the firstdielectric layer 406.

Referring to FIG. 6C, a patterned resist layer 604 is formed by alithography-and-patterning process. The patterned resist layer 604 fillsthe trenches 602 a and 602 c and overlies portions of the firstdielectric layer 406 disposed over the fin structures 102 a, 106 b.However, the trench 602 b is exposed (e.g. by an etching processconducted in conjunction with a patterning step of thelithography-and-patterning process). Referring to FIG. 6D, the powersupply line 101 b is formed in the trench 602 b. The barrier layer 412of the power supply line 101 b may be formed using a CVD process, suchas PECVD. The seed layer 414 of the power supply line 101 b may bedeposited by PVD, ALD, or CVD. The conductive material 416 of the powersupply line 101 b may be formed using any suitable deposition method,such as PVD, CVD, ALD, plating (e.g. electroplating), or a combinationthereof. Referring to FIG. 6E, following formation of the power supplyline 101 b, the patterned resist layer 604 is removed using, forexample, wet stripping or plasma ashing.

Referring to FIG. 6F, the trenches 602 a, 602 b, 602 c are filled with adielectric material 606 that is different from the material the firstdielectric layer 406. The dielectric material 606 also overlies portionsof the first dielectric layer 406 disposed over the fin structures 102a, 106 b. The dielectric material 606 includes one or more of thematerials described above in reference to fill fins 418 a, 418 b, 418 c.In a later step, the dielectric material 604 is patterned to form thefill fins 418 a, 418 b, 418 c. The dielectric material 604 may be formedby ALD, flowable CVD (FCVD), spin-on coating, or a combination thereof.A polishing process, such as a chemical mechanic polishing (CMP)process, is performed to planarize the top surfaces of the dielectricmaterial 606 and the first dielectric layer 406, thereby exposing topsurfaces of the fin structures 102 a, 106 b, as shown in FIG. 6G. Inessence, the polishing process removes excessive portions of thedielectric material 606 and the first dielectric layer 406 from the finstructures 102 a, 106 b.

Referring to FIG. 6H, the first dielectric layer 406 is selectivelyrecessed using, for example, dry etching, wet etching, RIE, and/or othersuitable etching methods. The selective recessing of the firstdielectric layer 406 is accomplished because of the difference in theetch rates of the material of the first dielectric layer 406 and thematerial of the dielectric material 606. The selective recessing of thefirst dielectric layer 406 defines the fill fins 418 a, 418 b, 418 c. Insome embodiments, such as in the example of FIG. 6H, the fin structures102 a, 106 b may also be subjected to etching, thereby reducing a heightof the fin structures 102 a, 106 b, as measured in the third direction(e.g. the z-direction). It is noted that even though the height of thefin structures 102 a, 106 b may be reduced, a top surface 605 of thepower supply line 101 b is still recessed in comparison to top surfaces603 of the fin structures 102 a, 106 b. The etching chemistries caninclude a fluorine-based fluid.

Referring to FIG. 6I, the source epitaxial feature 408 and drainepitaxial feature 410 are formed over the fin structures 102 a and 106b, respectively. In some embodiments, such as in the example of FIG. 6I,the fill fins 418 a, 418 b, 418 c may serve to self-align the epitaxialdrain feature 410 and the epitaxial source feature 408 to the drainregion of the fin structure 106 b and the source region of the finstructure 102 a, respectively. An epitaxy process used to form theepitaxial features 408 and 410 may include CVD deposition techniques(for example, vapor-phase epitaxy (VPE), ultra-high vacuum CVD(UHV-CVD), LPCVD, and/or PECVD), molecular beam epitaxy, other suitableSEG processes, or combinations thereof. The epitaxy process can usegaseous and/or liquid precursors. In the example of FIG. 6I, theepitaxial features 408 and 410 are doped with N-type dopants. It isnoted, however, that epitaxial features disposed in N-type well regionsof the integrated circuit device 100 are doped with P-type dopants. TheN-type epitaxial features 408 and 410 includes epitaxial layersincluding silicon and/or carbon, where silicon-containing epitaxiallayers or silicon-carbon-containing epitaxial layers are doped withphosphorous, arsenic, other N-type dopants, or combinations thereof (forexample, forming a Si:P epitaxial layer, a Si:C epitaxial layer, aSi:C:P epitaxial layer, a Si:As epitaxial layer, or combinationsthereof). On the other hand, the P-type epitaxial features of theintegrated circuit 100 includes epitaxial layers including siliconand/or germanium, where the silicon germanium containing epitaxiallayers are doped with boron, carbon, other P-type dopants, orcombinations thereof (for example, forming a Si:Ge:B epitaxial layer ora Si:Ge:C epitaxial layer).

Referring to FIG. 6J, the second dielectric layer 420 (e.g. ILD layer)is formed over the epitaxial features 408, 410 and fills the spacesbetween the epitaxial features 408, 410 and the first dielectric layer406 as well as the spaces between the epitaxial features 408, 410 andthe fill fins 418 a, 418 b, 418 c. The second dielectric layer 420additionally overlies the fill fins 418 a, 418 b, 418 c and theepitaxial features 408, 410. The second dielectric layer 420 may beformed using a suitable deposition process, for example, a PECVDprocess, an FCVD process, or other suitable deposition technique.

Referring to FIG. 6K, a lithography and etching process is performed toform a trench 608 (e.g. a slot opening) that exposes a portion of theepitaxial source feature 408 and a portion of the power supply line 101b. The etch process may be an anisotropic etch process that is tuned toselectively remove material of the second dielectric layer 420 andmaterial of the fill fin 418 b without etching the epitaxial sourcefeature 408. This may be accomplished by an anisotropic dry etchingprocess that uses a proper etching gas, such as fluorine-containing orchlorine-containing gas. As seen in FIG. 6K, a portion of the fill fin418 b proximate the epitaxial source feature 408 is removed in thisstep. It is noted that the epitaxial source feature 408 may function asan etch stop feature during the formation of the trench 608, with oneside of the trench being aligned to a fill fin (e.g. the fill fin 418a).

Referring to FIG. 6L, the source silicide layer 424 is formed byinitially depositing a metal layer over the epitaxial source feature408. The integrated circuit device 100 is then heated (for example,subjected to an annealing process) to cause constituents of epitaxialsource feature 408 (for example, silicon and/or germanium) to react withthe metal. Any un-reacted metal, such as remaining portions of the metallayer, is selectively removed by any suitable process, such as anetching process.

Referring to FIG. 6M, the source contact 314 is formed in the trench 608using, for example a deposition process. The barrier layer 502 of thesource contact 314 may be formed using a CVD process, such as PECVD. Theseed layer 504 of the source contact 314 may be deposited by PVD, ALD,or CVD. The conductive material 506 of the source contact 314 may beformed using any suitable deposition method, such as PVD, CVD, ALD,plating (e.g. electroplating), or a combination thereof. In someembodiments, the source contact 314 is etched back (e.g. such that itstop surface is recessed in comparison to a top surface of the seconddielectric layer 420) in order to reduce source contact to polycapacitance.

Referring to FIG. 6N, a lithography and etching process is performed toform an opening 610 that exposes one or more surfaces of the epitaxialdrain feature 410 using, for example, dry etching, wet etching, RIE,and/or other suitable etching methods. As shown in FIG. 6O, the drainsilicide layer 422 is formed on exposed surfaces of the epitaxial drainfeature 410 using similar processes discussed above in reference tosource silicide layer 424.

Referring to FIG. 6P, the drain contact 310 is formed in the opening 610using, for example, suitable deposition processes described above inreference to forming the source contact 314. At this point, it is notedthat this disclosure proposes forming the drain contact 310 and thesource contact 314 in separate steps, instead of a typical lithographyand etching process that includes initially forming a single continuousconductive structure in an opening and subsequently etching, cutting, orremoving a central portion of the single continuous conductivestructure, thereby resulting in the source contact 314 and the draincontact 310 having a separation of dimension D4. An effect of this isthat the proposed method has less constrained critical dimensionrequirements and process windows requirements in comparison to thetypical lithography and etching process described above. For example,instead of forming a cut window having an opening of dimension D4 (whichis less than 12 nanometers), the proposed method allows for a processwindow having an opening of dimension W2 (which is in a range from about15 nanometers to about 40 nanometers), thereby decreasing thepossibility of failure in the lithography and etching processes used toform the source contact 314 and the drain contact 310.

Referring to FIG. 6Q, the etch stop layer 426 is formed over the seconddielectric layer 420 and over the source and drain contacts 314, 310using a suitable deposition process, for example, a PECVD process, anFCVD process, or other suitable deposition technique. The via structure318 is formed in the etch stop layer 426 to contact the surface 310 a ofthe drain contact 310. The via structure 318 may be formed bylithography and etching process that initially forms an opening in theetch stop layer 426 and by a suitable deposition process that fills theopening in the etch stop layer 426 with a conductive material. Suitabledeposition processes include PVD, CVD, ALD, plating (e.g.electroplating), or a combination thereof. It is noted that the sequenceof steps discussed above in reference to FIGS. 6A to 6Q is not meant tobe limiting as the sequence may be different in other embodimentmethods. For example, in some embodiments, the epitaxial source anddrain features 408, 410 may be formed prior to the forming of the powersupply line 101 b.

FIG. 7 shows a flow chart illustrating a method 700 for formingtransistor devices of the array of standard cells of FIG. 1, inaccordance with an embodiment. The method 700 includes operation 702 offorming a first device fin structure and second device fin structure ona substrate, the first device fin structure being laterally adjacent tothe second device fin structure. The operation 702 may, as an example,include the steps discussed above in reference to FIG. 6A. The method700 includes operation 704 of depositing a first dielectric layerbetween the first device fin structure and the second device finstructure, the first dielectric layer defining a trench disposed betweenthe first device fin structure and the second device fin structure. Theoperation 704 may, as an example, include the steps discussed above inreference to FIG. 6B. The method 700 includes operation 706 of forming apower supply line in the trench. The operation 706 may, as an exampleinclude the steps discussed above in reference to FIGS. 6C to 6E. Themethod 700 includes operation 708 of forming a source feature and adrain feature on the first device fin and the second device fin,respectively. The operation 706 may, as an example, include the stepsdiscussed above in reference to FIGS. 6F to 61. The method 700 includesoperation 710 of forming a source contact to electrically couple thesource feature to the power supply line, the source contact including: afirst portion contacting a top surface of the source feature; and asecond portion extending towards the power supply line to physicallycontact the power supply line. The operation 706 may, as an example,include the steps discussed above in reference to FIGS. 6J to 6M.

In summary, the present disclosure proposes structural features for thesource contacts of the standard cells of the integrated circuit device100 that result in a decrease in parasitic capacitance between a sourcecontact and an adjacent drain contact, even as technology progressestowards smaller technology nodes. The structural features of the sourcecontacts of the standard cells of the integrated circuit device 100 alsolead to a decrease in a contact resistance between a respective sourcecontact and a respective power supply line to which the respectivesource contact is coupled. The decrease in parasitic capacitance and thedecrease in contact resistance also lead to an increase in an operatingspeed of the standard cells of the integrated circuit device 100.Furthermore, the present disclosure presents one or more embodimentmethods that may be used to form the embodiment source contacts. The oneor more embodiment methods have less constrained critical dimensionrequirements and process windows requirements in comparison to thetypical lithography and etching process described above.

An embodiment device includes: a first semiconductor strip extendinglongitudinally in a first direction; and a second semiconductor stripextending longitudinally in the first direction, the first semiconductorstrip and the second semiconductor strip being spaced apart from eachother in a second direction, the second direction being perpendicular tothe first direction. The device further includes a power supply linelocated between the first semiconductor strip and the secondsemiconductor strip in the second direction, wherein a top surface ofthe power supply line is recessed in comparison to a top surface of thefirst semiconductor strip; a source feature disposed on a source regionof the first semiconductor strip; and a source contact electricallycoupling the source feature to the power supply line. The source contactincludes: a lateral portion contacting a top surface of the sourcefeature; and a vertical portion extending along a sidewall of the sourcefeature towards the power supply line to physically contact the powersupply line.

An embodiment method includes: forming a first device fin structure anda second device fin structure on a substrate, the first device finstructure being laterally adjacent to the second device fin structure;and depositing a first dielectric layer on the first device finstructure and the second device fin structure, the first dielectriclayer defining a trench disposed between the first device fin structureand the second device fin structure. The method additionally includesforming a power supply line in the trench; forming a source feature anda drain feature on the first device fin structure and the second devicefin structure, respectively; and forming a source contact to couple thesource feature to the power supply line. The source contact includes afirst portion contacting a top surface of the source feature; and asecond portion extending from a peripheral region of the first portiontowards the power supply line to physically contact the power supplyline.

An embodiment device includes: a well region; a first transistor devicedisposed within a boundary of the well region, the first transistordevice including a first fin structure extending lengthwise in a firstdirection; a second transistor device disposed within the boundary ofthe well region, the second transistor device including a second finstructure extending lengthwise in the first direction, the firsttransistor device being spaced apart from the second transistor devicein a second direction, the second direction being perpendicular to thefirst direction. The device also includes an insulating region disposedbetween the first fin structure and the second fin structure in thesecond direction; a power supply line disposed within the insulatingregion, wherein the power supply line is recessed, in a third direction,in comparison to a source feature of the first transistor device, thethird direction being perpendicular to the first direction and thesecond direction; and a source contact coupling the source feature ofthe first transistor device to the power supply line. The source contactincludes a first portion disposed on a surface of the source featuredirected away from the well region; and a second portion extendingcontinuously from the first portion in the third direction to physicallycontact the power supply line.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A method, comprising: forming a first device finstructure and a second device fin structure on a substrate, the firstdevice fin structure being laterally adjacent to the second device finstructure; depositing a first dielectric layer on the first device finstructure and the second device fin structure, the first dielectriclayer defining a trench disposed between the first device fin structureand the second device fin structure; forming a power supply line in thetrench; forming a source feature and a drain feature on the first devicefin structure and the second device fin structure, respectively; forminga source contact to couple the source feature to the power supply line,the source contact including: a first portion contacting a top surfaceof the source feature; and a second portion extending from a peripheralregion of the first portion towards the power supply line to physicallycontact the power supply line.
 2. The method of claim 1, wherein a topsurface of the power supply line is recessed in comparison to the topsurface of the source feature.
 3. The method of claim 1, wherein formingthe source contact includes: forming a fill fin over the power supplyline, the fill fin being disposed between the source feature and thedrain feature; depositing a second dielectric layer over the firstdielectric layer, the source feature, the drain feature, and the fillfin; removing portions of the fill fin and the second dielectric layerto form a slot opening, the slot opening exposing the top surface of thesource feature and a portion of a top surface of the power supply line;and depositing one or more conductive materials in the slot opening. 4.The method of claim 3, wherein removing portions of the fill fin and thesecond dielectric layer to form the slot opening comprises ananisotropic etch process.
 5. The method of claim 4, wherein theanisotropic etch process uses a fluorine-containing etchant, achlorine-containing etchant, or a combination thereof.
 6. The method ofclaim 3, wherein a material of the fill fin is different from a materialof the first dielectric layer.
 7. The method of claim 1, wherein asidewall of the second portion of the source contact is aligned with asidewall of the power supply line.
 8. A method, comprising: providing aworkpiece comprising a first fin structure and a second fin structureover a substrate, the first fin structure being parallel to the secondfin structure; conformally depositing a first dielectric layer over thefirst fin structure, the second fin structure and the substrate todefine a trench between the first fin structure and the second finstructure; forming a conductive line in the trench; depositing a seconddielectric layer over the conductive line and the first dielectriclayer; selectively recessing the first dielectric layer to expose aportion of the first fin structure and a portion of the second finstructure; forming a first epitaxial feature over the exposed portion ofthe first fin structure and a second epitaxial feature over the exposedportion of the second fin structure; depositing a third dielectric layerover the first epitaxial feature and the second epitaxial feature; andforming a source/drain contact to couple the first epitaxial feature andthe conductive line.
 9. The method of claim 8, wherein the conductiveline comprises: a barrier layer in direct contact with the firstdielectric layer; a seed layer disposed over the barrier layer; and aconductive material disposed over the seed layer.
 10. The method ofclaim 9, wherein the conductive material comprises tungsten, althoughother suitable materials such as aluminum, copper, tungsten nitride,platinum, ruthenium, silver, gold, rhodium, molybdenum, nickel, cobalt,cadmium, zinc, or a combination thereof.
 11. The method of claim 8,further comprising: after the depositing of the second dielectric layer,planarizing the workpiece to expose the first dielectric layer and thesecond dielectric layer.
 12. The method of claim 8, wherein acomposition of the first dielectric layer is different from acomposition of the second dielectric layer.
 13. The method of claim 8,wherein the first dielectric layer comprises silicon oxides, siliconnitrides, silicon carbides, fluoro-silicate glass (FSG), low-Kdielectric materials, or a combination thereof wherein the seconddielectric layer comprises hafnium oxide, zirconium oxide, or aluminumoxide.
 14. The method of claim 8, wherein the selectively recessingforms a fill fin disposed directly over the conductive line.
 15. Themethod of claim 14, wherein the forming of the source/drain contactcomprises: forming an opening to expose the first epitaxial feature anda portion of the conductive line.
 16. The method of claim 15, whereinthe forming of the opening comprises removing a portion of the fill fin.17. A method, comprising: providing a workpiece that includes a firstfin and a second fin disposed side-by-side over a substrate; conformallydepositing a first dielectric layer over the first fin, the second finand the substrate to define a trench between the first fin and thesecond fin; forming a power supply line in the trench; depositing asecond dielectric layer over the power supply line and the firstdielectric layer; selectively recessing the first dielectric layer toexpose a portion of the first fin and a portion of the second fin;forming a source feature over the exposed portion of the first finstructure and a drain feature over the exposed portion of the second finstructure; forming a source contact to electrically couple the sourcefeature to the power supply line; and forming a drain contact directlyover the drain feature.
 18. The method of claim 17, wherein the draincontact is insulated from the power supply line.
 19. The method of claim17, further comprising: after the forming of the drain contact,depositing a fourth dielectric layer over the source contact and thedrain contact; and forming a drain contact via through the fourthdielectric layer to couple to the drain contact.
 20. The method of claim17, wherein the selectively recessing forms a fill fin disposed directlyover the conductive line, wherein a portion of the source contact isdisposed between the fill fin and the first dielectric layer.